Oswego climate

Oswego Frost Dates and Growing Season

NOAA 1991-2020 normals for Columbus, 23.7 km from Oswego, elevation 893 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Columbus. A median date has an even chance of a later freeze in spring, or an earlier one in fall.

The last spring freeze typically comes around April 5 and the first fall freeze around October 31, a growing season of about 208 days.

Median at 36°F
last April 16, first October 21
Median at 32°F
last April 5, first October 31
Median at 28°F
last March 25, first November 9

Last freeze in spring

The chance of a later freeze than the date shown. At 10 percent, one spring in ten still freezes after the date; planting after the 10 percent date for 32°F is the cautious choice.

Threshold10%20%30%40%50%60%70%80%90%
36°FMay 3Apr 29Apr 24Apr 20Apr 16Apr 12Apr 9Apr 5Mar 31
32°FApr 22Apr 16Apr 11Apr 8Apr 5Apr 2Mar 30Mar 26Mar 19
28°FApr 10Apr 5Apr 1Mar 29Mar 25Mar 21Mar 18Mar 13Mar 6
24°FMar 31Mar 26Mar 20Mar 17Mar 13Mar 9Mar 6Mar 2Feb 26
20°FMar 19Mar 13Mar 9Mar 6Mar 2Feb 28Feb 24Feb 20Feb 12
16°FMar 12Mar 6Mar 2Feb 28Feb 23Feb 18Feb 13Feb 6Jan 30

First freeze in fall

The chance of an earlier freeze than the date shown. At 10 percent, one fall in ten freezes before the date.

Threshold10%20%30%40%50%60%70%80%90%
36°FOct 6Oct 12Oct 16Oct 18Oct 21Oct 25Oct 27Oct 30Nov 3
32°FOct 18Oct 22Oct 26Oct 28Oct 31Nov 2Nov 5Nov 8Nov 14
28°FOct 26Nov 1Nov 3Nov 6Nov 9Nov 13Nov 16Nov 22Nov 28
24°FNov 2Nov 6Nov 11Nov 14Nov 19Nov 24Nov 29Dec 2Dec 8
20°FNov 9Nov 16Nov 22Nov 28Dec 1Dec 4Dec 9Dec 14Dec 21
16°FNov 21Nov 29Dec 3Dec 9Dec 13Dec 17Dec 22Dec 27Jan 5

Growing season length

Days between the last spring and first fall freeze at each threshold, with the chance of a season at least that long.

Threshold10%20%30%40%50%60%70%80%90%
36°F207200196192188183178173166
32°F229221217212208203199194187
28°F252244239233228224219214208
24°F275268261256251246240233226
20°F298290283277272267262255246
16°F324313305299294289283277267

How often it gets that cold

The share of years with at least one night at or below each temperature.

36°F or colder
100% of years
32°F or colder
100% of years
28°F or colder
100% of years
24°F or colder
100% of years
20°F or colder
100% of years
16°F or colder
100% of years

Degree days

A degree day is one degree of the daily mean temperature beyond a base, for one day. Heating degree days count cold (the fuel a house burns), cooling degree days heat, growing degree days the warmth a crop needs; each crop has its own base.

Heating degree days, base 65°F
4,342
Cooling degree days, base 65°F
1,553
Growing degree days, base 40°F
7,024
Growing degree days, base 45°F
5,646
Growing degree days, base 50°F
4,409
Growing degree days, base 55°F
3,316
Growing degree days, base 60°F
2,362

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January97807
February753020
March560594
April27824240
May90110488
June6304748
July0448913
August1419883
September36197611
October23142305
November547485
December863016

What this means

NOAA computes these from the daily lows at the station over 1991-2020, fitting the dates of each year's last and first freeze to a distribution, so a date can be stated at any level of risk. 36°F is a frost risk for tender plants on a clear, calm night, since the ground cools below the air above it; 32°F is a freeze; 28°F is a hard freeze that kills most annuals.

The station is 23.7 km from Oswego. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

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Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00141740 (Columbus). Public domain.